The Effect of Clipping on Net Photosynthesis and Dark Respiration Rates of Plants from an Upland Grassland, with Reference to Carbon Partitioning in Festuca ovina

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Abstract
Four co-existing species (Deschampsia flexuosa, Festuca ovina, Juncus squarrosus and Nardus stricta) were subjected to clipping and the net photosynthetic and dark respiration rates were followed after this treatment for 50 d. Concurrently carbon partitioning in F. ovina plants clipped initially and again at 50 and 100 d was examined. An expansion of new leaf lamina was observed with F. ovina, which had a greater net photsynthetic rate per unit leaf area than unclipped lamina. The remaining leaf lamina (stubble) after clipping also showed net photosynthetic and dark respiration rates greater than unclipped lamina; these responses were unique to F. ovina plants. N. stricta was the only other species to attain a pre-clipping photosynthetic rate within 6 d. Clipped F. ovina plants showed a change in carbon allocation pattern, with a reduction in carbon allocated to roots. 14C accumulated in roots and stubble was shown to have a role in regrowth, as was current assimilate via the production of new leaf lamina. Plants initially clipped before exposure to 14C, redistributed less 14C to new shoot growth and, therefore, lost less when subsequently clipped. Further redistribution of 14C came from leaf stubble tissue and not at the expense of roots. The variation between species in clipping response are discussed in terms of the implications for coexistence.